This research support contract will be used jointly by the laboratories of Dr. Ira Pastan (lab of molecular biology) and Douglas Lowy (Dermatology Branch). These two laboratories are seeking a combined contract because the technical requirements for each laboratory overlap considerably. This consolidation will represent an administrative savings to the Government and provide a more efficient use of the contractor who receives the award. The contract will support viral tumorigenesis studies in both labs. Dr. Pastan's laboratory has been investigating cellular transformation by the avian sarcoma viruses, while Dr. Lowy's laboratory is studying the biology of murine retroviruses and of papilloma viruses. Both laboratories have improved the sensitivity and specificity of experiments with these viruses through the use of molecularly cloned viral DNAs and highly specific anti-sera. This contract will facilitate the use of these and related reagents in both research programs.